1. Field of the Invention
The present invention relates to locks, especially electronic locks having motor-driven bolts. More specifically, the invention relates to locks in which it is desired that the bolt, once extended, cannot be forcibly pushed in but can only be withdrawn into the lock with entry of a proper combination or other authorization. The invention also relates to locks in which it is desired to respond to certain types of physical attack by rendering the bolt incapable of being withdrawn. The invention further relates to locks in which various security enhancements are provided.
2. Related Art
Numerous conventional lock designs have been provided in which a bolt may be extended or withdrawn in response to entry of a combination of other authorization. However, some of the designs have not provided a "dead bolt" feature, which involves physical blocking of the extended bolt so that, after the bolt has been extended into its "locked" position, the lock resists externally applied pressure that attempts to force the bolt back into the lock case.
Also, it is envisioned that locks are physically attacked in may ways, including drilling into the lock case. It is desired that a lock not merely physically resist such attacks, but also respond appropriately to such attacks by ensuring that the bolt cannot be withdrawn during or after the attack. In other words, it is desirable to prolong or perpetuate the "dead bolt" state so that in the event of physical attack, it becomes even harder for a perpetrator to gain entry into the protected area. Many known locks do not prolong or perpetuate a "dead bolt" state after the lock has been physically attacked, and thus do not provide adequate additional protection in that scenario.
Further, many known lock systems that involve "bolt works" require two separate actions to extend the blocking member from the door into the door jamb, and to re-extend the bolt from the lock case. This is not merely inconvenient, but presents an additional security risk should the individual neglect to perform the second action. Additionally, it is desirable in such systems to provide a "bolt throw" (extent of movement of the bolt) that is adjustable so as to easily adapt a single lock to a variety of installations and different types of bolt works.
Moreover, many known lock systems possess minimal locking functions, and do not provide additional security enhancement features. Applicants have recognized that such security enhancements include detection and response to tampering with the keypad unit, remote enablement and disablement of the lock, detection and response to a user's attempting to open the lock while under duress, and the ability to store and later transmit a history of occurrences in the lock system.
It is to meet these and other goals that the present invention is directed. No known conventional lock is believed to have the features and advantages of the inventive locks that are described in the following specification.